The Raptor 660 have, I purchased with a full FMF exhaust already installed. Since I have ridden it, I have noticed the heat on my right leg from the exhaust is quite hot, more so than I remember feeling on any other 660, or 700. It was to the point where I could not comfortably ride without boots, the heat was a bit much. Is this normal? Anyone out there with a full FMF system seeing this as well? Should it be running this hot?

 

You must be running lean. We measured the pipe temp on a 450 that had the same problem and his was around 700 degress F. I have a pipe on my 660 with no heat shield and mine doesn't get that hot, I would even be comfy riding in shorts.

 

I thought I may be running a lil lean, especially after reading the carb adjustment thread on here. Performance has been excellent, the only prob I have had is the heat, and it was more of a concern, than a problem.

 

Yeah a lean engine runs better than a rich one, but not for long! Did you re-jet it when you installed the pipe? If so waht jets and what filter/airbox lid combo do you have?

 

I never rejetted it after installing the pipe. When I purchased the ATV, the pipe was already installed. The previous owner did say that when he installed the pipe, it didnt seem like it was getting enough air. He drilled holes into the top of the airbox (WTF?!), to give it more air.

 

Oh my God!!!!!!! If he didn't rejet it, you better do so immediately and cross your fingers that you haven't done damage to your piston and cylinder walls!! Anytime you add more airflow, you need to rejet accordingly.

 

By "rejetting" do you mean adjusting the air mixture? Or physically removing the jets, to install larger ones? I understand the concept that an increase in air must be balanced with fuel as well, but can't this be done by adjusting air mixture to the richer side? Will it not adjust enough to compensate for additional airflow?

 

I just spoke with him, and no, it was never rejetted. So the question now is, how do I go about doing so? Can I just pick up a rejet kit at my yamaha dealer, or consult FMF to see what they recommend for the exhaust? FMF's recommendations, is a main jet of 145/150, stock needle, needle position = 3rd, and the fuel screw at 3. This sound correct?

 

Yeah you need a jet kit, or just buy a 145 and 150 jet, make the necessary adjustments, and save yourself some money.